The current and continuing trend in the telecommunications industry is toward providing a wide variety of information and communication services (hereafter "messaging services") over various communications networks to remote subscribers having diverse analog and digital communications equipment in an integrated fashion. Such communication services include, for example, voice messaging, facsimile messaging, wide area paging, electronic mail, electronic document interchange, interactive voice response, audio text, speech synthesis, speech recognition, video messaging/video mail, etc.
To provide these messaging services, different types of communications media from different types of communications equipment and processing protocols must be interfaced to a single host system or messaging center that provides the messaging services. For example, the host messaging center might notify a subscriber of various messages (e.g., pages, voice mail messages, etc.). To perform these services, protocol conversions must be performed between the format employed by the host messaging center and the various telecommunications formats employed by diverse subscriber equipment. One example is the protocol conversion between voice information received in pulse code modulated (PCM) format to/from a data compressed format in which the voice information is processed and stored at the host messaging center.
Companies that provide information services over the public telephone network generally use hardwired transceiving and protocol conversion equipment dedicated to a particular type of equipment and communications format/protocol. This dedicated hardware approach has obvious drawbacks in terms of cost, flexibility, and adaptability. For example, dedicated hardware cannot be readily modified to increase data throughput; nor can it be adapted to handle communication protocols corresponding to new telecommunication equipment and services. To support multiple type of messaging services to a diverse set of communications equipment, costly replacements and new hardwire designs of dedicated hardware are required.
More recently, digital signal processing has been used to process a digital communications trunk line as described for example in U.S. Pat. No. 4,991,169 to Davis et al. Unfortunately, even though the digital signal processing in Davis adds some flexibility in converting different types of signal formats, it lacks sufficient channel handling capacity and data throughput for large scale and/or sophisticated multi-media messaging applications. While Davis might be suitable for some very simple conversion algorithms such as DTMF detection and a low capacity system, Davis' system is severely limited with respect to the number of communication channels that can be handled. Nor can Davis' system perform different protocol conversion processes in parallel. Moreover, Davis lacks the ability to dynamically change the protocol conversion algorithm executed by the DSP system in real time while still processing channels.
What is needed is a multi-media interface that overcomes these deficiencies in terms of much increased handling and throughput capacity and increased system adaptability/flexibility to different communication media types to provide subscribers with a variety of multi-media communications options in real time.
The present invention provides a multi-media interface (MMI) that universally and flexibly supports present (and contemplated) messaging applications including voice mail, facsimile mail, electronic mail, interactive voice response, DTMF tone detection, automated attendant services, audio text services, radio paging services, speech recognition/speech synthesis, voice recognition, video messaging, video mail, common channel signalling, short messaging services, etc. The MMI interfaces multi-media voice and data between various communication networks including for example the public switched telephone network (PSTN), the packet switched public data network (PSPDN), and the cellular telephone and paging networks at a very high data throughput. In order for the host messaging center to provide these services to multi-media subscribers communicating over various communications networks, the multi-media interface makes necessary protocol conversions for different telecommunications protocols corresponding to various types of telecommunications media (and associated control signalling) which may include, for example, speech in analog form, speech data in pulse code modulated (PCM) form, modem data in PCM form, data in analog form modulating sinusoidal carriers, and data in various digital forms associated with a variety of protocol standards. A programmable line interface module and a time slot interchanger frame the received information and selectively route various time slots of information from the communications network to/from multiple parallel digital signal processors (DSPs) (each with its own dual port, high speed RAM) to perform various protocol conversions. A local central processing unit (CPU) controls and coordinates the line interface, time slot interchanger, and DSPs via a local bus in accordance with commands from the host messaging center.
The programmable line interface module links subscriber communications information received from a communications network through time division multiplex (TDM) channels (or time slots) corresponding to digital carrier systems for North American (T1) and European (E1) standards. The line interface module frames and synchronizes the incoming raw data, PCM voice, modem, and other media formats and routes that information to the time slot interchanger which then connects a particular time slot channel to one of the multiple, parallel digital signal processors, e.g. six. Functioning as the interface between the host messaging center and digital carrier channels routed through the time slot interchanger, the DSPs perform virtually any kind of necessary protocol conversion so that the information can be processed and stored in the protocol format of the host. For example, incoming quantized voice samples in A-PCM or .mu.-PCM format may be converted using regular pulse excitation long term prediction (RPE-LTP) algorithms into a compressed data format used by the host messaging center.
The multiple parallel digital signal processors operate completely independently of each other and communicate with the local CPU via the local CPU bus using their dedicated, dual port RAMs. In response to channel service requests from time slots over multiple time division multiplex communication lines, each DSP individually processes in parallel multiple time slots of information in the process of handling channel service requests. As a result, in an example where each DSP performs a voice protocol conversion algorithm such as that just described for six time slots, if six parallel DSPs were all processing voice in this manner, the MMI would be handling thirty-six time slots simultaneously.
At initial system configuration and also in real time (if system needs demand), the local CPU dynamically allocates one or more of the DSPs to handle different types of protocol conversions for multiple communications channels. For example, with each digital signal processor processing multiple time slots of information at one time (i.e. six or seven time slot channels for each TDM frame), five DSPs could be configured to handle voice conversion processing for twenty-five voice channels, and one DSP could be configured to handle protocol conversions for five facsimile channels.
Depending upon what services are required by a particular caller, the local CPU downloads appropriate protocol conversion algorithms from the host messaging center to a selected one or more DSPs using a service configuration table that is downloaded from the host messaging center. Taking a high level example in a voice mail context, if a caller presses a DTMF button during a voice prompt indicating a Group III facsimile service request, the host messaging center commands the MMI to route this Group Ill facsimile call to one or more of the DSPs currently configured to provide the necessary protocol conversions for Group III facsimile. In this way, the converted facsimile information can be stored in data compressed binary form in the host messaging center under the caller's mailbox identification number.
If a caller wishes to interact with the host messaging center via interactive voice rather than pushbutton or keyboard and that service is not presently being supported by one of the DSPs, the appropriate voice recognition and voice synthesis software is downloaded from the host center to one or more of the DSPs via a VME interface, the local CPU, and the DSP's corresponding dual port RAM. The DSP(s) is(are) then configured with the necessary software to perform the protocol conversions required so that the host messaging center and caller can interact by voice. Other software may be similarly downloaded in real time to any of the multiple DSPs to ensure that other messaging services such as voice mail, facsimile mail, etc. are provided to multiple diverse subscribers with fast and efficient protocol conversion.
Because the architecture of the multi-media interface is modular, it is readily adaptable to handle any other types of protocols to permit handling of new data and providing of new messaging/telephony services without changing its basic architecture. For example, more parallel DSPs could be added to provide greater capacity, greater throughput, and/or new types of call services requiring new protocol conversions. In addition, the DSPs can be configured in real time to adapt to system needs so that if more data processing capacity is now required for an increase in facsimile related services and voice related services are down, one or more DSPs could be removed from voice protocol conversion and dedicated to facsimile protocol conversion. Alternatively, the DSPs could be replaced with other processing hardware more suited to a particular application. And as described above, if a new communications medium is added to the system, e.g. video image signals for video conferencing, the corresponding protocol conversion software is readily downloaded into one or more of the parallel DSPs to accommodate these new communications medium signals.